1. Field of the Invention
The present invention relates to a dye-containing negative curable composition, a color filter using the dye-containing negative curable composition, a method of producing the same, and a solid-state image sensor.
2. Description of the Related Art
A pigment dispersion method is widely known as a method of producing a color filter used in liquid crystal displays (LCD) and solid-state image sensors (CCD, CMOS and the like).
The pigment-dispersion method is a method of producing a color filter by a photolithographic method using a colored photosensitive composition having a pigment dispersed in various photosensitive compositions. Since patterning is conducted by the photolithographic method, this method is considered to be suitable for producing a large-sized color filter having high positional accuracy and high resolution. In the pigment-dispersion method, a color filter is obtained by repeating a process for each color, the process including forming a coating film by applying a photo-sensitive composition onto a glass substrate by a spin-coater or a roll-coater, forming a colored pixel by exposing the coating film to light in a pattern-wise manner, and developing the exposed coating film.
In preparation of a display device such as an LCD, CCD or CMOS using a color filter including a pigment, reduction in particle size of the pigment has been demanded from the viewpoint of improving the contrast (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2000-321763). This is because a polarizing axis may be rotated by scattering of light, double-refraction, or the like due to the pigment. When the size of the pigment is not small enough, light may be scattered and absorbed, light transmittance may be lowered, and the contrast may be lowered. Moreover, curing sensitivity upon pattern-exposure may be degraded.
Demands for further increase in resolution have recently been particularly high in a color filter used in solid-state image sensors. However, further improvements in resolution have become difficult to achieve in a conventional pigment-dispersion system, since there are problems such as occurrence of color irregularities due to coarse particles of a pigment. Therefore, the pigment-dispersion system has been unsuitable for applications in which a fine pattern with a pixel size of as small as 1.5 to 3.0 μm square is required, such as solid-state image sensors.
With the view of overcoming the above situation, a technique of using a dye instead of a pigment has been proposed. Further, in recent years, reduction in thickness of a colored pattern (for example, 1 μm or less) has been required for improving image quality by increasing light-harvesting properties and light-color separating properties. In order to reduce the thickness of the colored pattern, concentration of a dye has to be increased in view of maintaining color density. On the other hand, as the concentration of the dye increases, sensitivity may greatly decrease, the pattern may easily exfoliate in a region at which the exposure amount is low, or the shape of the pattern may be distorted upon baking at high temperature after the formation of the pattern, thereby failing to maintain the originally formed shape of the pattern.
In order to overcome the above-mentioned problems, a method in which the amount of an initiator is increased has been known.
As techniques relevant to the above, JP-A No. 2006-119441 discloses a photothermal polymerizable composition containing a polymerizable compound having a triazine skeleton and a heteroalicyclic block isocyanate compound having a triazine skeleton in combination. Further, JP-A No. 8-62841 discloses a photosensitive resin composition containing isocyanuric acid ethylene oxide-modified tri(meth)acrylate as a photopolymerizable compound.
However, when the amount of the initiator is increased, generation of a remnant may be significant. Further, the shape of the pattern may be distorted to a tapered shape upon heating at high temperature, such as post-baking, thereby failing to obtain a rectangular shape. This distortion tends to be significant particularly in the formation of a fine pattern of 2 μm square or less (for example, a Bayer pattern of 1.5 μm square or less).
Moreover, in the techniques of using a composition including a compound having an imide structure containing a carbonyl group, such as the aforementioned heteroalicyclic block isocyanate compound or isocyanuric acid ethylene oxide-modified tri(meth)acrylate, distortion of a pattern due to heating cannot be prevented. In particular, it is difficult to form a fine pattern having a size of as small as 2 μm square or less with a desired rectangular shape.
The present invention has been made in view of the above problems, and provides a dye-containing negative curable composition that can suppress distortion of a pattern caused by heating after patterning, a color filter that can suppress distortion of a pattern caused by heating and maintain a favorable shape (in particular, a rectangular shape for solid-state image sensors), a method of producing the color filter, and a solid-state image sensor having excellent color reproducibility.
The present invention has been made based on the findings that when a polymerizable compound, which serves to cure the composition, has basicity and a structure capable of interacting with an acidic group or an ester group in the composition, tolerance of the composition against heat that is applied after exposure and curing (patterning) can be improved.